A windsurfing spot for learning needs to be safe and flat. The location must have a safe launching area and it must offer protection if a windsurfer falls and starts to drift downwind etc. Try in winds not lighter than 5 knots and not stronger than 10 knots. Wind that is too light will hinder the feel of the sail and your balance, wind too strong will make learning frustrating.
Speak to the locals, ask about currents, tides and prevailing winds. Go to places where there are other windsurfers sailing, you don't want to be the only person on the water when learning.
The wind direction must be blowing onshore for it to be the safest, this means that if you stand on the shore facing the water the wind blows directly into your face, if it's blowing against your back then this is an offshore wind. Offshore wind is the most dangerous wind direction for beginners to learn windsurfing, it will literally blow you out to sea.
Side onshore wind is also a save wind and sometimes a side-shore is fine provided there is a bank or something similar to catch you if you drift down wind.
Opt for shallow water at first as this will help with your confidence, oh, and warm water.
Be sure there is no boat traffic, check for rocks and coral or other hazards that might put you into the way of danger.